linux-kernel - Re: RFC for a new Scheduling policy/class in the Linux-kernel

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Message-ID: <4A5CCD5A.80108@nortel.com>
Date:	Tue, 14 Jul 2009 12:24:26 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Raistlin <raistlin@...ux.it>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Douglas Niehaus <niehaus@...c.ku.edu>,
	Henrik Austad <henrik@...tad.us>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Bill Huey <billh@...ppy.monkey.org>,
	Linux RT <linux-rt-users@...r.kernel.org>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	"James H. Anderson" <anderson@...unc.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ted Baker <baker@...fsu.edu>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Noah Watkins <jayhawk@....ucsc.edu>,
	KUSP Google Group <kusp@...glegroups.com>,
	Tommaso Cucinotta <cucinotta@...up.it>,
	Giuseppe Lipari <lipari@...is.sssup.it>
Subject: Re: RFC for a new Scheduling policy/class in the Linux-kernel

Raistlin wrote:

> Remember that all my points are concerned with budgets, i.e., a scenario
> where you have some mean to limit the capability of a task to ask for
> CPU time over some kind of period.
> And here it is where the problem comes since running C instead of having
> A busy waiting means:
> - that A is actually blocked, as said before;

Why does it make any difference that A is blocked rather than busy
waiting?  In either case A cannot make forward progress.

> - that A's budget is not diminished.

If we're running B with A's priority, presumably it will get some amount
of cpu time above and beyond what it would normally have gotten during a
particular scheduling interval.  Perhaps it would make sense to charge B
what it would normally have gotten, and charge the excess amount to A?

Chris
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